Figure 3.

The polymer pEt_20 potentiates rifampicin in various types of Gram‐negative bacteria including MDR strains (E. coli, E. C., E. aerogenes, E. A., K. pneumoniae, K. P., and A. baumannii, A. B.). * Symbol indicates MDR strains. a) MICs and MBCs of rifampicin with and without polymer. The use of pEt_20 led to 256‐ to 2048‐fold and 128‐ to 512‐fold reduction in rifampicin MIC and MBC, respectively. pEt_20: 7.8 µg mL⁻¹ (0.5× MIC). b) Three‐compartment plates with bacteria treated by pEt_20, rifampicin or pEt_20/rifampicin combination for 18 h. 1) A. baumannii (ATCC BAA‐1709), 2) A. baumannii (ATCC 179 606), 3) A. baumannii (ATCC BAA‐1789), 4) A. baumannii (ATCC BAA‐1792). The combination was bactericidal (≥99.9% killing efficiency) against all bacterial strains tested, while pEt_20 or rifampicin did not kill the bacteria (≈0% killing efficiency as compared to that at 0 h) when used alone. No bacterial colonies were seen in the groups treated by the combination. The concentration of pEt_20 in (b) 0.5× MIC, i.e., 7.8 µg mL⁻¹ for all A. B. strains and E. C., 15.6 µg mL⁻¹ for E. A. and K. P. MIC and MBC data are representative of three biological replicates.